Exam 4: The Study of Chemical Reactions

Consider the reaction (CH₃)₃CBr + CH₃CH₂OH → (CH₃) ₃COCH₂CH₃ + HBr. Experimentally one finds that if the concentration of (CH₃)₃CBr is tripled, the rate of the reaction triples. One also finds that if the concentration of CH₃CH₂OH is doubled, the rate of the reaction is unchanged. Which of the following correctly describes the kinetics of this reaction?

Chlorination of methane can result in a mixture of chlorinated products. What experimental conditions should be used to favor the production of chloromethane over the other chlorinated products?

Given a reaction in which reactant A is converted only to product B at 25°C, what K_eq results if at equilibrium 80% of A has become B?

Which of the following correctly expresses the standard Gibbs free energy change of a reaction in terms of the changes in enthalpy and entropy?

Provide the major organic product(s) in the reaction below.

When compound I, C₇H₁₆, was treated with chlorine and light it yielded 3 monochlorination products that could be separated by chromatography. Two of the products were primary alkyl halides and the other was a secondary alkyl halide. Provide a possible structure for compound I.

Explain the significance of the frequency factor A in the Arrhenius equation.

Provided the following pK_a values for the two acids below, draw an energy diagram for the acid-base reaction. Be sure to label each axis correctly.

Which of the following reactive intermediates can best be described as both nucleophilic and strongly basic?

Write an equation to describe the initiation step in the chlorination of methane.

A certain free radical chlorination reaction of 2,3-dimethylbutane leads to the production of two major monochlorinated products 1-chloro-2,3-dimethylbutane and 2-chloro-2,3-dimethylbutane. When run through a Gas chromatograph, it was determined that the product distribution was 51.7% 1-chloro-2,3-dimethylbutane and 48.3% 2-chloro-2,3-dimethylbutane. If we assign the primary H's a reactivity of 1.0, what is the relative reactivity of the tertiary H's?

The chlorination of methane is characterized by a high quantum yield. Explain what this means.

Given a DG° of -8.0 kJ/mol at 25°C, calculate the corresponding K. [R = 8.314 J/K∙ mol]

Consider the three-step mechanism for the reaction of A through intermediates B and C to produce D shown below. A → B E_a = 15 kcal/mol, ΔH° = 13 kcal/mol B → C E_a = 10 kcal/mol, ΔH° = -6 kcal/mol C → D E_a = 2 kcal/mol, ΔH° = -20 kcal/mol Which of the three steps is rate-limiting?

Which of the following is $\underline{\text{ not }}$ a possible termination step in the free radical chlorination of methane?

What reactive intermediate is formed when CHBr₃ is treated with hydroxide or when diazomethane is irradiated?

Given the bond dissociation energies below (in kcal/mol), calculate the overall ΔH° for the following reaction: (CH₃)₃CH + Br₂ → (CH₃)₃CBr + HBr (CH₃)₃C-H 91 (CH₃)₃C-Br 65 Br-Br 46 H-Br 88 CH₃-Br 70

Consider the reaction: CH₃CH₂∙ + Br₂ → CH₃CH₂Br + Br∙ . Given that this reaction has an activation energy of +6 kcal/mol and a ΔH° of -22 kcal/mol, sketch a reaction-energy diagram for this reaction. Label the axes and show E_a and ΔH° on your drawing.

Within the visible spectrum, it has been experimentally determined that blue light is the most effective in initiating the chlorination of methane. What is the mechanistic significance of this observation?

Consider the reaction of A being converted into B at 25°C. If the ΔG° of this reaction is the K_eq is ________ and the % conversion is ________.